1. Field of the Invention
The invention relates to methods of fabricating integrated circuits, and more particularly to a method of improving the formation of a thin film of solid material during the fabrication of integrated circuits by selective deposition of a precursor liquid on a surface having nonuniform surface properties.
2. Statement of the Problem
The manufacture of integrated circuits entails series of numerous steps in which layers of materials are sequentially deposited, patterned, and etched to form the various components of the circuit.
One of the problems associated with integrated circuit manufacture is that thin film layers, once deposited, must usually be patterned and etched using complex, multistep processes. The patterning and etching processes are time-consuming and expensive; furthermore, the etching mechanisms to remove certain layers often cannot be exactly controlled, resulting in damage to the integrated circuit and in decreased manufacturing yields.
3. Solution to the Problem
The invention solves the problems associated with patterning and etching processes by providing a method for selectively depositing a thin film of solid material on an integrated circuit substrate. According to the method of the invention, a thin film of solid material is formed only on a selected portion of the substrate. As a result, no patterning and etching of the thin film is necessary to remove it from unselected portions.
The thin film of solid material is selectively formed on only a selected portion of the substrate, and is not formed on another portion of the substrate, by selecting the substrate portions so that they are different in at least one physical property, and selecting the deposition process so that the thin film will form on the portion of the substrate with a selected physical property and will not form on the portion of the substrate having the different physical property.
In a preferred embodiment, the method of the invention comprises: providing a substrate having a substrate surface, such that the substrate surface has a first substrate surface and a second substrate surface; providing a precursor liquid for forming a liquid coating on the substrate surface such that the liquid coating will have a surface tension suitable for wetting the first substrate surface and unsuitable for wetting the second substrate surface; applying the precursor liquid to the substrate surface to form the liquid coating; and treating the liquid coating on the substrate surface to form the thin film of solid material on the first substrate surface.
The invention provides a method of fabricating a thin film of solid material in an integrated circuit, comprising steps of: providing a substrate having a first substrate surface and a second substrate surface, the first substrate surface having at least one physical property that is different than the corresponding physical property of the second substrate surface; selecting a precursor liquid and a precursor liquid deposition process such that applying the precursor liquid to the first and second substrates using the liquid deposition process will form a solid thin film on the first substrate surface upon treating of the liquid precursor and will not form a solid thin film on the second substrate surface upon treating of the liquid precursor; applying the precursor liquid to the substrate using the liquid deposition process to coat the substrate; and treating the coating on the substrate to form the thin film of solid material on the first substrate surface. Preferably, the method further includes the step of cleaning the substrate to remove residues from the second substrate surface without removing the thin film of solid material from the first substrate surface. Preferably, the step of cleaning comprises washing the substrate. Preferably, the step of selecting a precursor liquid comprises selecting a precursor liquid that will more readily wet the first surface than the second surface. Preferably, the step of selecting a precursor liquid comprises selecting a precursor liquid including a solvent selected from the group comprising HMDS and dioxane. Preferably, the step of selecting a precursor deposition process comprises selecting a process from the group comprising spin coating and misted deposition. Preferably, the step of selecting a precursor deposition process comprises selecting a misted deposition process and further includes the step of selecting a range of droplet sizes for the mist such that the droplets will more readily stick to the first surface than the second surface. Preferably, the step of selecting a precursor deposition process comprises selecting a misted deposition process and further includes the step of selecting a deposition rate such that a solid thin film will be formed on the first surface and a solid film will not be formed on the second surface. Preferably, the first surface comprises a conductive material and the second surface comprises an insulating material. Preferably, the conductive material is selected from the group consisting of platinum, iridium, ruthenium, palladum, tungsten, titanium tungsten, metal silicides, tantalum nitride, aluminum titanium nitride, and titanium nitride. Preferably, the insulating material is selected from the group consisting of silicon oxides, silicon nitrides, silicon oxynitrides and silicon oxyfluorides. Preferably, the first surface comprises a material having tensile stress and the second surface comprises a material having compressive stress. Preferably, the step of treating comprises a process selected from the group consisting of: exposing to vacuum, exposing to ultraviolet radiation, electrical poling, drying, heating, baking, rapid thermal processing, and annealing.
In another aspect, the invention provides a method of fabricating a thin film of solid material in an integrated circuit, comprising steps of: providing a substrate having a first substrate surface and a second substrate surface, the first substrate surface being a surface on which a thin film of a solid material will tend to form upon application of a precursor liquid to the first substrate surface and treating of the precursor liquid, and the second substrate surface being a surface on which a thin film of a solid material will tend not to form upon application of the precursor liquid to the second substrate surface and the treating of the precursor liquid; applying the precursor liquid to the substrate; and treating the precursor liquid on the substrate to form the thin film of solid material on the first substrate surface. Preferably, the method further includes the step of cleaning the substrate to remove residues from the second substrate without removing the thin film of solid material from the second substrate. Preferably, the step of cleaning comprises washing the substrate. Preferably, the precursor liquid is selected from the group consisting of HMDS and dioxane. Preferably, the first surface comprises a conductive material and the second surface comprises an insulating material. Preferably, the conductive material is selected from the group consisting of platinum, iridium, ruthenium, palladum, tungsten, titanium tungsten, metal silicides, tantalum nitride, aluminum titanium nitride, and titanium nitride. Preferably, the insulating material is selected from the group consisting of silicon oxides, silicon nitrides, silicon oxynitrides and silicon oxyfluorides. Preferably, the first surface comprises a material having tensile stress and the second surface comprises a material having compressive stress. Preferably, the step of applying is selected from the group consisting of spin coating and misted deposition. Preferably, the step of treating comprises a process selected from the group consisting of: exposing to vacuum, exposing to ultraviolet radiation, electrical poling, drying, heating, baking, rapid thermal processing, and annealing.
In a further aspect, the invention provides a method of fabricating a thin film of solid material in an integrated circuit, comprising steps of: providing a substrate having a substrate surface, the substrate surface having a wetting portion and a nonwetting portion; providing a precursor liquid for forming a liquid coating on the substrate surface such that the liquid coating will have a surface tension suitable for wetting the wetting portion and unsuitable for wetting the nonwetting portion; applying the precursor liquid to the substrate surface to form the liquid coating; and treating the liquid coating on the substrate surface to form the thin film of solid material on the wetting portion. Preferably, the thin film of solid material comprises a metal oxide, and most preferably, a layered superlattice material or silicon dioxide. Preferably, the precursor liquid comprises a metal compound, and preferably, the metal compound is selected from the group consisting of metal 2-ethylhexanoates and metal 2-methoxyethoxides, and the solvent is selected from the group consisting of alcohols, aromatic hydrocarbons, and esters. Preferably, the method further comprises a step of washing the substrate surface to remove undesired material from the nonwetting portion.
In yet a further aspect, the invention provides an integrated circuit comprising: a first layer comprising a first material having a first surface; a second layer comprising a second material, having a second surface; a third layer comprising a third material formed over the second layer; the first, second and third layers meeting at a junction region; and the first surface having a first portion adjacent to and on one side of the junction region, a second portion adjacent to and on the other side of the junction region from the first portion, the first and second portions of the first surface being level with one another. Preferably, the third layer is formed directly on the second layer.
The method according to the invention not only permits the reduction in the number of process steps needed to fabricate an integrated circuit, but also results in high quality thin films that are useful for sensitive integrated circuit applications. Numerous other features, objects and advantages of the invention will become apparent from the following description when read in conjunction with the accompanying drawings.